在BESIII实验上寻找最轻的粲偶素混杂多重态

Conventional charmonium states are well described by quark potential models. However, there is still no position for many of these newly discovered charmonium-like mesons in the conventional charmonium spectrum. There is growing evidence that at least some of these new states are exotic, i.e. new forms of hadronic matter such as mesonic-molecules, tetraquarks, or hybrid mesons. The understanding of these states is primarily at the level of conjecture, thus further experimental input is crucial for understanding of the charmonium-like states. As the first discovered 1-- vector exotic state, Y(4260) is always in the central position of charmonium-like field. The most popular interpretation on the property of Y(4260) is taking it as a candidate of heavy hybrid meson. Many models conclude hybrids with the quantum numbers (0,1,2)-+ and 1-- form the lightest hybrid supermultiplet. The pattern of Y(4260) with quantum numbers (0,1,2)-+ exist if Y(4260) is taken as a 1--charmonium hybrid meson. It’s crucial to search them in experiment to confirm the hybrid theory. Based on data samples collected with the BESIII detector at the BEPCII collider at center-of-mass energies from 4.2 to 4.6 GeV, we search for the hybrid pattern of Y(4260), (0,1,2)-+, via hadronic transitions (0,1,2)-+→eta chi_cJ and pi+pi- chi_cJ.

夸克模型很好的描述了粲偶素能谱，但是实验上发现的一系列类粲偶素粒子却不能被夸克模型所解释。越来越多的证据显示这些粒子并不是常规的类粲偶素，而可能是如分子态，四夸克态，和混杂态等。关于类粲偶素的属性还都处于猜测阶段，还没有确凿的证据证实任何一项理论解释。作为第一个在实验上被发现的JPC=1--的类粲偶素，最流行的关于Y(4260)的属性的解释认为它是一个混杂态。很多混杂态模型预言量子数为(0,1,2)-+ 和 1--的粒子组成质量最轻的混杂多重态。如果Y(4260)是一个混杂态，那么寻找它的另外三个伴随态对混杂态模型的证实至关重要。本项目是在BESIII实验上利用4.2-4.6能区的数据寻找Y(4260)的混杂伴随态(0,1,2)-+，而这些混杂态在实验上的重建则通过强子衰变(0,1,2)-+→eta chi_cJ 和 pi+pi- chi_cJ实现。

X(3872)粒子作为实验上发现的最重要的一个类粲偶素粒子，关于其属性的研究一直是强子领域的前沿课题。利用北京正负电子对撞机上运行的北京谱仪III实验于2020-2021年在质心系能量4.66-4.946 GeV能区采集的数据我们首次观测到了e+e-→ ω X(3872)过程。我们一共观测到了24.6±5.3 个信号，信号显著性达到8.0 σ. 利用不同能量点的信号产额，我们测量了e+e-→ ω X(3872)的产生截面和X(3872)->π+ π- J/ψ衰变分之比乘积随不同能量点的分布。这是世界上首次发现此e+e-→ ω X(3872)的产生过程，将为X(3872)粒子属性的研究提供重要的实验信息。